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Ferlavirus infection


Synonym(s): Ophidian paramyxovirus, OPMV

Introduction

  • Cause: ferlavirus, an enveloped RNA virus with a negative-strand RNA genome.
  • Signs: usually neurorespiratory but signs may involve other organ systems.
  • Diagnosis: PCR testing, hemagglutination inhibition test (HI), virus isolation, gross pathology and histopathology.
  • Treatment: supportive and symptomatic treatment.
  • Prognosis: poor to grave.

Presenting signs

  • Clinical signs are variable.
  • Peracute form: sudden death with no previous signs.
  • Acute form: anorexia Anorexia, regurgitation, respiratory signs including gaping and blood or a brownish discharge emerging from the glottis, and terminally, neurological signs such as head tremors, flaccid paralysis or convulsions.
  • Chronic form: a history of anorexia and regurgitation and are weak and emaciated and have poor muscle tone.
  • Over a period of several months they may develop diarrhea and respiratory and neurological signs

Geographic incidence

  • Ferlavirus infection has been described in snakes, chelonia and lizards in Europe, the Americas and the Canary Islands but is likely distributed worldwide.

Age predisposition

  • Geriatric snakes may be more susceptible than younger animals.

Breed/Species predisposition

  • Ferlavirus has been isolated from all the major snake families including elapids, boids, colubrids, viperids, and crotalids.
  • Very few reports of ferlavirus in reptiles other than snakes show a correlation between disease and infection with the virus.
  • However, there are insufficient data to rule out the possibility that lizards, chelonians and maybe even crocodiles, play important roles as reservoirs for ferlavirus.

Public health considerations

  • No known zoonotic risks.

Cost considerations

  • Diagnostic testing.
  • Cost of culling valuable collections.

Special risks

  • Heightened anesthetic risk in snakes with respiratory signs.

Pathogenesis

Etiology

  • Family: Paramyxoviridae.
  • Subfamily: Paramyxovirinae.
  • Genus: Ferlavirus.

Predisposing factors

General

Specific

  • Ferlavirus is spread by aerosol and contact.
  • Transmission via direct contact with respiratory secretions.

Pathophysiology

  • Most commonly seen gross pathological changes: pulmonary congestion or edema, hemorrhagic pneumonia Pneumonia, free blood in the oral cavity or coelom, mucoid or caseous exudate in the lung, diffuse to focal accumulations of caseous necrotic debris in pulmonary tissue.
  • Histological lesions may be classified according to organ systems:
    • Respiratory:
      • Lung: full of macrophages, exudate and cellular debris.
      • Epithelial cells: hypertrophy, hyperplasia and metaplasia; pale eosinophilic intracytoplasmic inclusion bodies.
      • Pulmonary septa: thickened with edema fluid and infiltrated with mixed inflammatory cells; occasional giant cells.
      • Interstitium: varying amounts of mixed inflammatory cells.
    • Neurological:
      • Brainstem and upper spinal cord: occasional demyelination, degeneration of axon fibers and ballooning of axon sheaths; eosinophilic intracytoplasmic inclusions in glial cells; eosinophilic intranuclear inclusions in neurons.
      • Brain: perivascular cuffing.
    • Other tissues:
      • Pancreas: hyperplasia of acinar cells and terminal duct epithelium; pancreatic necrosis and/or fibrosis.
      • Liver: intracytoplasmic inclusion bodies. Hepatic necrosis, necrosis of the bile ducts and pyogranulomatous hepatitis in some cases.
      • Esophagus: lymphohistiocytic neuritis.

Timecourse

  • The incubation period of ferlavirus in naturally acquired infections is unknown.

Epidemiology

  • The shedding patterns of ferlavirus are unknown.
  • There are no controlled studies to support any claims regarding the existence of persistently-infected shedding state or of snakes that mount an appropriate immune response and have cleared the infection.
  • It is reasonable to assume that ferlavirus can be transmitted between snakes by both oral secretions and cloacal excretions. There are currently no reports concerning vertical transmission of ferlavirus; however, there is evidence for vertical transmission of another paramyxovirus Sunshinevirus infection.
  • The incubation period of ferlavirus in naturally acquired infections is unknown.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hyndman T H, Shilton C M & Marschang R E (2013) Paramyxoviruses in reptiles: A review. Vet Micro 165, 200-213 PubMed.
  • Hyndman T H, Shilton C M, Doneley R J & Nicholls P K (2012) Sunshine virus in Australian pythons. Vet Micro 161 (1-2), 77-87 PubMed.

Other sources of information

  • Solis C, Arguedas R, Baldi M et al (2017) Seroprevalence and Molecular Characterization of Ferlavirus in Captive Vipers of Costa Rica. J Zoo Wild Med 48(2), 420-430.
  • Jacobson E R (2007) Viruses and Viral Diseases of Reptiles. In: Infectious Diseases and Pathology of Reptiles. Ed: Jacobson E R. CRC Press, USA. pp 395-460.
  • Ritchie B (2006) Virology. In: Reptile Medicine and Surgery. 2nd edn. Ed: Mader D. Saunders Elsevier, USA. pp 391-417.

Organisation(s)

  • Association of Reptile and Amphibian Veterinarians. Website: www.arav.org.